Italian engineers propose to desalinate sea water with solar energy
FAO estimates that by 2025, nearly 2 billion people on Earth will suffer deficit of clean potable water to meet their daily needs.
Desalination of sea water may be a possible solution to this problem. Of course, water supply via desalination is quite energy-consuming business, because such it needs 10 thousand times more energy than a simple pumping and purification of river or underground water. Therefore, scientists decided to reduce the cost of removing dissolved salts from water by using solar energy.
A team of engineers from the Department of Energy of Politecnico di Torino, Italy, studied this issue. They developed a prototype of a solar distiller to desalinate seawater in a sustainable and inexpensive way. Such technologies have already been proposed in the past, but compared to previous solutions, innovation from Italian researchers is actually able to double the useful output – in this case, drinking water.
The principle of operation of the device is very simple and is inspired by the plant mechanism of transpiration, i.e. the process of water movement along the capillarity and its evaporation through the external organs of the plant, such as leaves, stems and flowers.
So, engineers from Torino have created a floating device from inexpensive porous material - in fact a floating sponge – which is made of two hydrophilic layers. They "absorb" sea water, without expensive bulky pumps. The collected sea water is heated by solar energy, supporting the process of salt separation and water evaporation begins under the influence of heat. The process is facilitated by membranes inserted between drinking water and contaminated water, preventing the two from mixing.
The desalination device is based on spontaneous processes that take place without the help of auxiliary equipment, and therefore can be called passive technology. All this makes the unit inherently inexpensive and easy to install, as well as attractive to the population of coastal areas, usually suffering from a lack of drinking resources. It is also proposed to equip floating gardens with such desalinator, this is especially useful for densely populated areas.
The only known disadvantage of passive distillation technologies was their low energy efficiency. However, scientists from Torino approached this obstacle in a creative way. Their latest efforts have focused on how to maximize the absorption of solar energy, and, as a result, they have achieved record levels of productivity - 20 litres per day of drinking water per square meter exposed to the sun.
After the prototype of the solar desalination plant has been successfully tested in the sea waters – in the Ligurian sea, the researchers of Politecnico di Torino are looking for possible industrial partners to launch their technoproduct into wide production and make it more durable, scalable and versatile.
